Animorphs is a science fantasy series of youth books written by Katherine Applegate and her husband Michael Grant, writing together under the name K. A. Applegate, and published by Scholastic. It is told in first person, with all six main characters taking turns narrating the books through their own perspectives. Horror, war, imperialism, dehumanization, sanity, morality, innocence, leadership, freedom, family, and growing up are the core themes of the series.

Katherine Alice Applegate, known professionally as K. A. Applegate, is an American young adult and children's fiction writer, best known as the author of the Animorphs, Remnants, and Everworld book series. She won the 2013 Newbery Medal for her 2012 children's novel The One and Only Ivan. Applegate's most popular books are science fiction, fantasy, and adventure novels. She won the Best New Children's Book Series Award in 1997 in Publishers Weekly. Her book Home of the Brave has won several awards. She also wrote a chapter book series in 2008–09 called Roscoe Riley Rules.